基于MODIS-NDVI的区域冬小麦遥感估产——以山东省济宁市为例

以黄淮海平原冬小麦主产区山东省济宁市为研究实例,利用遥感方法,采用250 m分辨率经过Savitzky-Golay滤波技术平滑处理的MODIS-NDVI遥感数据对冬小麦产量进行预测.研究选取了冬小麦关键生育期内0.2～0.8范围的旬NDVI数据,并建立了其与冬小麦产量的关系.同时,采用逐步回归方法筛选建立冬小麦关键生育期旬NDVI与冬小麦产量间关系的估产模型.利用地面实测冬小麦产量数据,对所建的估产模型进行精度检验,结果表明,估产相对误差在-3.6％～3.9％之间.表明利用Savitzky-Golay滤波技术平滑后的作物关键生育期内MODIS-NDVI遥感数据进行冬小麦估产,其方法精度较高,具有一定的可行性.     

中国北方草地与农牧交错带植被的NDVI-Ts空间的年内变化特征

利用多时相或时序植被指数(normalize difference vegetation index,NDVI)数据进行地表覆盖研究已取得了大量成果。随着陆地表面温度(1and surface temperature,TS)遥感反演精度的不断提高,将Ts与NDVI结合起来进行地表植被动态变化的监测已成为可能。本文主要包括以下三部分内容：1)介绍了基于卫星遥感数据的NDVI、Ts和Ts／NDVI计算方法。2)讨论NDVI、Ts和Ts／NDVI数据对植被覆盖信息表达的差异,并分析了中国北方草地与农牧交错带植被在NDVI-TS空间的年内变化特征。3)利用信息熵和平均梯度,定量分析了NDVI、Ts和Ts／NDVI数据在信息表达丰富度方面的差异,并对在不同地表植被覆盖下,Ts／NDVI数据对信息提高程度的敏感性进行了讨论。     

中国北方草地与农牧交错带植被的NDVI-Ts空间的年内变化特征

利用多时相或时序植被指数(normalize difference vegetation index,NDVI)数据进行地表覆盖研究已取得了大量成果.随着陆地表面温度(1and surface temperature,Ts)遥感反演精度的不断提高,将Ts与NDVI结合起来进行地表植被动态变化的监测已成为可能.本文主要包括以下三部分内容:1)介绍了基于卫星遥感数据的NDVI、Ts和Ts/NDVI计算方法.2)讨论NDVI、Ts和Ts/NDVI数据对植被覆盖信息表达的差异,并分析了中国北方草地与农牧交错带植被在NDVI-Ts空间的年内变化特征.3)利用信息熵和平均梯度,定量分析了NDVI、Ts和 Ts/NDVI数据在信息表达丰富度方面的差异,并对在不同地表植被覆盖下,Ts/NDVI数据对信息提高程度的敏感性进行了讨论.     

浙江省作物多熟种植制度遥感反演及其时空格局

结合作物物候特征,利用2001-2010年的MODIS/NDVI时间序列数据,在基于改进的Savitzky -Golay滤波算法重构高质量序列的基础上,对浙江省作物熟制进行遥感反演,并分析了浙江省作物熟制的时空格局变化特征.结果表明:空间分辨率为250 m的16 d合成MODIS/NDVI时间序列数据能够准确定量地反演出作物熟制的时空格局;NDVI峰值集中出现于每年的2-3月、5-6月和8-9月;浙江省作物种植以一年二熟制为主,从2001-2010年的种植情况来看,一年二熟作物种植面积最大,年际变化幅度较小,一年一熟和一年三熟作物种植面积相当,年际变幅相对较大;2001年以来浙江耕地复种指数整体呈缓慢增加趋势,2010年复种最大为205.5,但距其潜力理论值288仍有一定距离,表明浙江复种潜力仍较大,耕地利用程度有待提高.     

农作物遥感估产最佳时相的选择研究——以中国主要粮食作物为例

最佳时相遥感图象的选择是农作物遥感估产的关键环节之一,它必须兼顾作物识别和单产模拟对遥感时相选择的要求,综合考虑多方面的影响因素,根据农作物遥感估产中各项工作的具体要求,以提高遥感图象中目标作物信息及其与作物单产关系的显著程度为主要目的,分析了农作物遥感估产最佳时间的选择依据,认为它主要包括作物光谱的种间差异、作物物候的种间差异、太阳高度角的变化,作物产量形成的关键期、作物面积泽收获面积的代表性以     

基于多源遥感数据的大豆叶面积指数估测精度对比

近年来遥感技术的革新促使遥感源越来越丰富.为分析多源遥感数据的叶面积指数(LAI)估测精度,本文以大豆为研究对象,利用比值植被指数(RVI)、归一化植被指数(NDVI)、土壤调整植被指数(SAVI)、差值植被指数(DVI)、三角植被指数(TVI)5种植被指数,结合地面实测LAI构建经验回归模型,比较3类遥感数据(地面高光谱数据、无人机多光谱影像以及高分一号WFV影像)对大豆LAI的估测能力,并从传感器几何位置和光谱响应特性以及像元空间分辨率三方面分析讨论了3类遥感数据的LAI反演差异.结果表明:地面高光谱数据模型和无人机多光谱数据模型都可以准确预测大豆LAI(在α=0.01显著水平下,R~2均0.69,RMSE均0.40);地面高光谱RVI对数模型的LAI预测能力优于无人机多光谱NDVI线性模型,但两者差异不大(E_A相差0.3%,R~2相差0.04,RMSE相差0.006);高分一号WFV数据模型对研究区内大豆LAI的预测效果不理想(R~20.30,RMSE0.70).针对星、机、地三类遥感信息源,地面高光谱数据在反演LAI方面较传统多光谱数据有优势但不突出;16 m空间分辨率的高分一号WFV影像无法满足田块尺度作物长势监测的需求;在保证获得高精度大豆LAI预测值和高工作效率的前提条件下,基于无人机遥感的农情信息获取技术不失为一种最佳试验方案.在当今可用遥感信息源越来越多的情况下,农业无人机遥感信息可成为指导田块精细尺度作物管理的重要依据,为精准农业研究提供更科学准确的信息.     

基于无人机高清数码影像和高光谱遥感数据反演大豆典型生育期氮平衡指数

氮平衡指数(NBI)是反映作物长势的重要指标之一.通过测量NBI可以快速监测作物氮肥盈亏状况,为农业生产和管理提供精准信息.本文以无人机高清数码影像和高光谱遥感数据,以及地面实测大豆NBI数据为基础,分析大豆从开花期到成熟期,原始光谱和红外、近红外波段的导数光谱与NBI的相关性,筛选敏感波段并计算植被指数.采用经验模型法构建NBI反演模型,通过分析验证模型的决定系数(R^2)和均方根误差(RMSE),得出最佳反演模型.结果表明:大豆NBI与导数光谱反射率的相关性好于与原始光谱反射率的相关性;本文筛选的14个植被指数中,除了导数光谱光化学植被指数与大豆NBI呈不显著相关外,其余13个植被指数与大豆NBI呈极显著相关;利用13个植被指数构建NBI反演模型,并分析模型反演精度,结果显示,利用导数光谱差值植被指数构建NBI反演模型的精度最高,R^2和RMSE分别为0.771和3.077,利用该模型生成大豆典型生育期NBI分布图,能够反映大豆的长势状况.通过多载荷无人机获取的高清数码影像和高光谱遥感数据进行NBI估算,能够实时、动态、非破坏性、快速有效地监测大豆氮素营养状况,可为大豆氮肥精确管理提供简便实用的方法.     

基于地面高光谱和GF-1卫星的区域花生LAI估算

掌握作物叶面积指数(LAI)及其动态变化对于作物生长监测和估产等有重要意义。利用地面高光谱数据进行作物生长参数的反演是农业遥感研究的热点,但其中大多是利用地面高光谱数据建立作物LAI的估算模型研究,难以进行区域化应用。为把地面高光谱研究结果应用到卫星尺度,实现区域花生LAI的反演,从而对大面积花生长势进行监测,本文利用GF-1卫星传感器的光谱响应函数和地面高光谱数据,在试验站小区试验和大田试验基础上,基于地面观测光谱数据构建多种宽波段光谱指数,建立基于高光谱指数的花生LAI遥感估算模型。通过比较估算模型的决定系数和验证精度,认为基于RVI指数建立的模型(LAI=0.481RVI^0.830)是LAI估算的最佳模型。基于最优模型进行花生LAI遥感制图,获得花生LAI分布情况。利用野外试验观测数据验证遥感反演LAI精度,结果表明,利用宽波段指数和GF-1适用于花生LAI估算,对今后进行大面积花生长势监测有重要意义。     

利用亚像元尺度信息改进区域冬小麦生长的模拟

为了探寻遥感观测面尺度与作物模型模拟点尺度不匹配问题的解决方案并改善区域作物生长模拟精度,以河南省鹤壁市为研究区,以冬小麦为研究对象,基于MODIS、Landsat 8遥感数据和Wheat SM作物生长模型,通过MODIS LAI过程线重建、亚像元尺度信息提取、集合卡尔曼滤波同化等方法,进行了冬小麦生长模拟的研究。结果表明:通过MODIS LAI过程线重建并提取亚像元尺度信息,冬小麦纯度在80%以上的遥感反演LAI与冬小麦两个关键生育期实测冠层LAI的均方根误差(RMSE)为0.69,以最近邻域法赋值到整个模拟区域,研究区2013—2017年模拟总产和实际总产相比的RMSE在未同化遥感反演的LAI信息时为6.73×108kg,同化未利用亚像元尺度信息调整的遥感估算LAI时,RMSE上升到8.24×108kg,同化利用亚像元尺度信息分区赋值的遥感LAI时,RMSE下降到3.48×108kg。利用亚像元尺度信息生成与作物模型时空尺度匹配的格点化LAI遥感产品,可提高作物生长模型区域化应用的精度。     

利用遥感信息研究西藏地区主要植被年内和年际变化规律

利用1982～2000年NOAA-AVHRR月合成NDVI遥感资料和相关气象台站数据对我国西藏地区的稀疏草地、浓密草地和Tebit森林等主要植被的变化进行了初探。利用月合成NDVI的多年平均值分析了植被指数年内季节性变化规律及其与气候因子的关系,利用多年月合成NDVI的标准差描述了NDVI年际间波动情况。结果表明,在西藏地区,浓密草地和Tebit森林的NDVI植被指数年内变化规律呈明显的季节性,而稀疏草地则不明显;在年际变化方面,浓密草地月合成NDVI值波动幅度最大,Tebit森林次之,稀疏草地最小,且波动幅度较大的月份集中在NDVI值较高的植被生长季节6～10月份。     

黑土长期施肥及养分循环再利用的作物产量及土壤肥力质量变化Ⅱ.养分在作物体内分配

根据黑土长期肥料试验1985～1995年期间的作物分析资料,研究了施肥和作物生长状况对大豆、玉米、小麦3种作物体内养分浓度、养分在籽实和秸秆中分配比以及形成1000kg籽实产量的收获养分量等参数的影响,结果表明,在本试验的正常施肥条件下,上述参数十分稳定,受施肥和作物生长状况的影响不大,可直接用于这一地区养分收支的估算     

黑土长期施肥及养分循环再利用的作物产量及土壤肥力质量变化Ⅱ、养分在作物体内分配

根据黑土长期肥料试验1985－1995年期间的作物分析资料,研究了施肥和作物生长状况对大豆、玉米、小麦3种作物体内养分浓度、养分在籽实和秸秆中分配比以及形成1000kg籽实产量的收获养分量等参数的影响,结果表明,在本试验的正常施肥条件下,上述参数十分稳定,受施肥和作物生长状况的影响不大,可直接用于这一地区养分收支的估算。     

辽西半干旱地区农田水分循环特征的研究Ⅰ.农田供水状况研究

探讨辽西半干旱地区的农田供水状况．分析表明该区大田作物的耗水来源主要为生长期内大气降水和土壤储水,由于大气降水不足,特别是生长前期的严重缺水是该地区作物减产的一个重要原因,而且还经常出现伏旱和“秋吊”,大气降水占作物耗水量的７５．６％以上,而土壤供水量最高达作物耗水量的２４．４％,作物耗水量与生长期内大气降水呈直线关系．     

辽西半干旱地区农田水分循环特征的研究 Ⅰ. 农田供水状况研究

探讨辽西半干旱地区的农田供水状况。分析表明该区大田作物的耗水来源主要为生长期内大气降水和土壤储水,由于大气降水不足,特别是生长前期的严重缺水是该地区作物减产的一个重要原因,而且还经常出现伏旱和“秋吊”, 大气降水占作物耗水量的75.6%以上,而土壤供水量最高达作物耗水量的24.4%, 作物耗水量与生长期内大气降水呈直线关系。     

玉米地垄沟种平菇培肥地力的研究——Ⅱ培肥地力的效果

本文描述了微生物的分析方法以及在培养平菇以后,后茬作物平均增产10％以上,能连续两年获得粮食稳定高产。     

Tracking pyrethroid resistance in the polyphagous bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae), in the shifting landscape of a cotton-growing area

In cotton-growing areas of Central Africa, timing of host crops and pest management practices in annual rainfed cropping systems result in a shifting mosaic of habitats that influence the dynamics and resistance of Helicoverpa armigera (Hübner) populations on spatial scales, both within and across seasons. From 2002 to 2006, regional and local resistance was monitored among cotton fields and among the major host plants of the bollworm. From 2002, pyrethroid resistance increased within and across cotton-growing seasons to reach a worrying situation at the end of the 2005 growing season. Cotton crops played a fundamental role in the increase in seasonal resistance, even if the intensive use of insecticides on local tomato crops strongly concentrated resistance alleles in residual populations throughout the off-season. Due to the relative stability of resistance in H. armigera populations despite a long off-season, we believe that after the dispersal of the moths southwards at the end of the growing season, reverse migration mainly accounts for the reconstitution of populations at the onset of the following growing season. In addition, local resistance monitoring in 2005 and 2006 showed that it was possible to control the increase in resistance by temporarily stopping the use of pyrethroids during the period of peak infestation of cotton by H. armigera. On the other hand, the similar resistance frequency of populations sampled from sprayed and unsprayed synchronous hosts confirmed the absence of reproductive isolation between adults. As a result, diversity in cropping systems should be encouraged by planting alternative host plants to provide a mosaic of habitats, which in return would provide insecticide-free refuges. The implications for insecticide resistance management in annual cropping systems are discussed.     

The efficacy of sex-attractant monitoring for the pea moth, Cydia nigricana, in England, 1980–1985

SUMMARY
The efficacy of monitoring the pea moth ( Cydia nigricana ) in dry-harvested pea fields with pheromone traps was evaluated on commercial farms in Eastern England used by ADAS as back-up monitoring sites. In particular the use of a 'threshold' catch to determine both the need for and timing of insecticide sprays was evaluated. Fields in which 'threshold' catches were achieved had more damage in unsprayed plots than fields in which there were no 'threshold' catches. When two sprays were applied to crops at 'threshold' sites, the timing of the first predicted by the monitoring system, excellent control was achieved with 85% of crops having less than 1% peas damaged, and none more than 2–3%. Incorrectly timed sprays, or even one correctly timed spray, produced erratic control.
Simple assessments of economic loss show that it is unnecessary to spray crops in which a 'threshold' is not achieved. Spraying 'threshold' crops, however, is very worthwhile and applying two sprays, the first timed with pheromone traps, will be particularly advantageous to both growers of peas for human consumption when 'clean' crops are at a premium, and to seed producers.
The data can be used to predict the probabilities of damage levels, assuming different control strategies.     

Dynamics of CO2 efflux from the substrate root system of container-grown plants associated with irrigation cycles

In intensive horticultural crops, the choice of growing media and the adequate management of irrigation must ensure an optimal trade-off between aeration and water supply to roots. The proportion of gas-filled pores and their composition can be strongly affected by the water status and hence by irrigation. In this context, continuous measurement of gas exchange and water status of the growing medium could bring out some insights into how irrigation events affect root activity and aeration in a time scale of minutes to several hours. For this purpose, a measuring system was developed that measured the CO₂ efflux rate from the entire substrate root system of pot plants while their shoots were kept outside, undisturbed. It was able to monitor four plants at a time for several weeks at a rate of one measurement per plant every 10 min, thus tracing the dynamics of CO₂ efflux through a great many irrigation cycles. The results showed a marked pattern of CO₂ efflux around each irrigation event, consisting mainly of a sharp, conspicuous peak followed by a depression until a threshold in substrate water potential was reached. Analysis of these data suggests that the pattern is imposed mainly by the effects of irrigation and water content on the mobility of gases in the growing medium. The peak can be explained by the CO₂-enriched air being displaced by the water added to the growing medium in the pot, and the following depression can be the result of the reduced mobility of gases when substrate water content is high. In spite of the great variation in the instantaneous efflux rate of CO₂, the integration of these CO₂ values for the entire day provides a rather predictable value given the root biomass and does not seem to be affected by the number of irrigation events that occur in a given day.     

Carbon assimilation in crops at high temperatures

Global temperatures are rising, and higher rates of temperature increase are projected over land areas that encompass the globe's major agricultural regions. In addition to increased growing season temperatures, heat waves are predicted to become more common and severe. High temperatures can inhibit photosynthetic carbon gain of crop plants and thus threaten productivity, the effects of which may interact with other aspects of climate change. Here, we review the current literature assessing temperature effects on photosynthesis in key crops with special attention to field studies using crop canopy heating technology and in combination with other climate variables. We also discuss the biochemical reactions related to carbon fixation that may limit crop photosynthesis under warming temperatures and the current strategies for adaptation. Important progress has been made on several adaptation strategies demonstrating proof‐of‐concept for translating improved photosynthesis into higher yields. These are now poised to test in important food crops.     

Lignocellulosic‐based bioenergy and water quality parameters: a review

High rates of crop residue removal as biofuel feedstocks could increase losses of nonpoint source pollutants, negatively affecting water quality. An alternative to residue removal can be growing dedicated bioenergy crops such as warm season grasses (WSGs) and short‐rotation woody crops (SRWCs). Yet, our understanding of the implications of growing dedicated bioenergy crops on water quality is limited. Thus, we (i) synthesized and compared the impacts of crop residue removal, WSGs, and SRWCs on water quality parameters (i.e., sediment and nutrient runoff, and nutrient leaching) and (ii) identified research gaps for growing dedicated energy crops. Literature indicates that residue removal at rates >50% (residue retention up to 4.71 Mg ha^?1) can increase runoff by 5–15 mm, sediment loss by 0.2–7 Mg ha^?1, NO₃–N by 0.58–1 kg ha^?1, and sediment‐associated C by 0.3–57 kg ha^?1 per rainstorm event compared to no residue removal. Crop residue removal may also increase nutrient leaching. Studies on the impacts of growing WSGs as dedicated bioenergy crops at field scale on water quality parameters are few. However, WSGs when used as conservation buffers reduce losses of sediment by 66–97%, nutrients by 21–94%, and contaminants by 9–98%. This suggests that if WSGs were grown as dedicated bioenergy crops at larger scales, they could reduce losses of nonpoint source pollutants. Literature indicates that SRWCs can consistently reduce NO₃–N leaching. More modeled than field data are available, warranting further field research on (i) field data collection from WSGs and SRWCs from marginal lands, (ii) growing monoculture or polyculture of WSGs, and (iii) large‐scale production of energy crops. Overall, dedicated bioenergy crops, particularly WSGs, can reduce losses of nonpoint source pollutants compared to residue removal and be an important strategy to improve water quality if grown at larger scales.